Jim Fuller Caltech/KITP ACOUSTIC OSCILLATIONS IN RED GIANTS

QUIZ: IN WHICH DECADE WAS THE FIRST PULSATING RED GIANT DISCOVERED? Answer: 1596 Mira’s variability discovered by David Fabricious

LUMINOSITY VARIATIONS FROM ACOUSTIC OSCILLATIONS

Chaplin & Miglio 2013

WHAT ARE ACOUSTIC OSCILLATIONS? Sound waves in star Waves are excited by convective motions Sound waves reflect, create global-scale standing waves, i.e., oscillation modes, at characteristic frequencies

CHARACTERISTIC FREQUENCIES Stellar dynamical frequency Freefall frequency, orbital frequency at stellar surface

CHARACTERISTIC FREQUENCIES Acoustic cutoff frequency Characteristic atmospheric frequency

OSCILLATION FREQUENCIES Stars tend to oscillate at frequencies Oscillation spectrum exhibits peaks separated by

SPHERICAL HARMONICS l m

Chaplin & Miglio 2013

EVOLUTION UP GIANT BRANCH As stars evolve up RGB or AGB, their radii increase dramatically Mode frequencies and frequency spacing decrease Longer observation baselines needed Continuous data not needed Mode amplitudes increase Less sensitivity needed to detect oscillations

Mosser et al. 2013

SCALING RELATIONS Chaplin & Miglio 2013

LOWER RED GIANT BRANCH Chaplin & Miglio 2013

ROTATIONAL SPLITTING Mosser et al. 2012

UPPER RED GIANT BRANCH Mosser et al. 2013

POWER OF PTF PTF has ability to detect oscillations in lots (millions?) of red giants With measurement of mode frequencies and spacings, PTF can characterize these stars Provides synergy with K2, GAIA, TESS, PLATO, LSST, etc.